Obstructive Sleep Apnea
Definitions, pathophysiology, and epidemiology: body mass index (BMI) used to define obesity; weight in kilograms divided by square of height in meters; morbid obesity defined as BMI >35; many patients not in healthy weight range; obesity increasing dramatically in United States (eg, from 1991 to 1998, percentage of obese people doubled in state of Maryland); obesity much more of risk factor for morbidity than mortality; obese tend to have increased cardiovascular disease, type 2 diabetes mellitus, cancer (eg, of colon), osteoarthritis, work disability, and sleep apnea; conditions result in operating room (OR) visits for coronary artery bypass graft (CABG) and for hip and knee replacement; analysis of Baltimore Longitudinal Study of Aging (BLSA; average age approximately 80 yr) found that men tend to be a little narrower, women tend to be more widely spread, both literally and figuratively, in terms of BMI; looked at relationship between obesity and mortality in elderly; found that high BMI does not predict mortality in elderly Comorbidities: those associated with obesity and sleep apnea include hypertension, accidents (eg, automobile, industrial), right heart failure and cor pulmonale, coronary artery disease, and insulin resistance; of adults with sleep apnea, at least 70% obese Prevalence of sleep-disordered breathing in middle-aged adults: obesity greatest predictor; increases with age; more common in men than women; five times greater incidence in minorities (especially Hispanics) compared to whites; in absence of sleep study, question bed partner about history (eg, pauses, apnea, obstruction) Interventions for sleep apnea: behavioralweight loss; avoidance of alcohol and sedatives; exercise; nocturnal positioning (to help maintain patency of airway); gastric bypass does a great job of reducing some of these airway problems and the sleep apnea problems that obese patients have; medicalfirst-line therapy involves continuous positive airway pressure (CPAP); oral appliances second-line therapy; others antidepressants, thyroid hormone (in hypothyroid patient), and nocturnal O2 Continuous positive airway pressure: patients can bring their own to surgery; use during monitored anesthesia care (MAC); use postoperatively; patients knowledgeable about CPAP Congestive heart failure (CHF) and central sleep apnea: thought that those with CHF become hypoxic, hyperventilate, drop PCO 2 , and become apneic; nocturnal O2 reduces apnea-hypopnea index CHF and obstructive apnea: one study showed that simulated obstructive sleep apnea (OSA) in patients with CHF resulted in larger decrease in blood pressure than in normal patients; clearly a downward spiral you dont want to get yourself into; give O2 and consider airway devices (eg, CPAP) Common surgical procedures: gastric bypass, orthopedic surgery, laparotomy or laparoscopy, tracheostomy (in extreme situation), uvulopalatopharyngoplasty, and genioglossal advancement Airway management: consider laryngeal mask airway (LMA), awake endotracheal intubation, fiberoptic intubation, positioning, preoxygenation, and agents of choice; study comparing sniffing position with simple head extension for laryngoscopic view in elective surgery found sniffing position not helpful, except in obese patient; another study showed that CPAP enhanced preoxygenation in morbidly obese women; although concerns exist about using LMA on obese patient who may have risk factors for reflux, when the chips are down, this is an important part of our armamentarium in these patients Predicting difficult intubation in obese patient: one study showed that in morbidly obese patient, high Mallampati score does not predict poor laryngoscopic view; authors suggested that perhaps a new method is needed to predict difficult intubation in morbidly obese patients Volatile anesthesia: study compared different anesthesia techniques for laparoscopic surgery in morbidly obese; 36 patients randomized to desflurane, isoflurane, or propofol anesthesia; time to eye opening, extubation, and stating name faster with less soluble volatile anesthetic; helpful to use drugs that are metabolized quickly or eliminated quickly; even when using Bispectral Index (BIS) to titrate anesthesia, morbidly obese patients awoke more quickly with less-soluble volatile anesthetic Maximize nonnarcotic analgesia: large amounts of opioids may result in problems with postoperative O2 desaturation and apnea; give local anesthesia before, during, and after; peripheral nerve blocks may be useful; spinals and epidurals (may be technically challenging); nonsteroidal anti-inflammatory drugs (NSAIDs); alpha2 -adrenergic agonists Postoperative analgesia: even patient-controlled analgesia (PCA) can be challenging in these patients (due to possible O2 desaturation; these people you want to send to the floor on O2 ); may be necessary to have patient in more monitored setting or have nurse administer; morbidly obese tend to have decreased perioperative tissue oxygenation (may lead to development of postoperative wound infection); despite technical difficulties, regional anesthesia safe alternative for obese and morbidly obese patients; giving epidural or spinal opiates may be particularly problematic in obese patient; abstract from Ramsey shows dexmedetomidine improves postoperative pain management in surgical patients Intensive care unit (ICU) overnight: abstract from Mayo Clinic found that OSA not independent risk factor for unanticipated hospital admission, or for adverse perioperative events in outpatient surgery; patients may be managed as outpatients for nonairway surgery Conclusion:take good history; encourage CPAP; be prepared; reverse Trendelenburg position; short-acting drugs; encourage regional anesthesia and analgesia; maximize nonnarcotic analgesia; be prepared for postoperative problems (consider prolonged postanesthesia care unit [PACU] or ICU; consider invasive monitoring)
(Audiodigest Anesthesia 2003)
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